What cellular structure distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells are distinguished from prokaryotic cells primarily by the presence of a nucleus. The nucleus is a membrane-bound structure that houses the cell's genetic material, or DNA, allowing for more complex regulation of gene expression and cellular processes. This compartmentalization enables eukaryotic cells to perform specialized functions and manage their genetic information more effectively than prokaryotic cells, which lack a nucleus and instead have their DNA located in a region called the nucleoid.

The presence of a nucleus is a fundamental characteristic that contributes to the complexity and variety of eukaryotic cells, which can make up multicellular organisms like plants and animals, unlike prokaryotic cells, which are typically single-celled organisms such as bacteria. This distinction is crucial in understanding cellular organization and the evolutionary differences between these two domains of life.